1. Field of the Invention
This invention relates to an ink jet head, and, more particularly, to an ink jet head for generation of small ink droplets for recording to be used for the so-called ink jet recording system.
2. Description of the Prior Art
An ink jet head to be applied for the ink jet recording system is generally provided with minute ink discharging outlets (orifices) having apertures of several tens .mu. to 100.mu. in diameter, ink flow paths and portions for generating ink discharging pressure provided at a part of said ink flow paths.
As the method for preparing such an ink jet head, there has been known, for example, a method in which minute grooves are formed, by way of cutting or etching, on a plate of a glass or a metal, and then the plate having such grooves is bonded to another appropriate plate for formation of ink flow paths.
However, a head obtained according to the method as described above suffers from a drawback that straight driving characteristic of ink droplets discharged has frequently been impaired. This is due, after all, to the difference in wetting characteristics at the orifice peripheral for the ink, because the orifice of the head is formed of materials having different qualities.
In addition to the above fact, when discharging of an ink has been carried out for a long time or vibration is applied to a head, the ink leaked out from the orifice may be adhered to a part of the orifice circumference and then combined to form an ink pool, which will attract the ink droplets discharged toward its direction, thereby impairing straight driving characteristic of ink droplets.
In the prior art, in order to overcome such an inconvenience, it has been proposed to prepare separately a flat plate provided with orifice by forming an orifice on a flat plate (e.g., a metal plate or a photosensitive glass plate) by etching thereof (this is hereinafter referred to as "orifice plate") and then attaching the orifice plate onto a head body to give an ink jet head.
According to this method, however, an orifice is formed by etching and therefore strains may be formed in the orifices obtained due to the difference in the degree of etching, or the shapes of orifices may vary considerably, whereby it is difficult to prepare an orifice plate which is very precise. Thus, the ink jet head prepared by this method has the drawback that straight driving characteristic of the ink droplets discharged could not be sufficiently improved.
Further, in the above method, an orifice plate is required to be attached to a head body. During such an operation, dimensional precision is liable to be less. In addition, there are other disadvantages such as the adhesive employed in this operation may flow into orifices or ink flow paths which are very minute to effect clogging thereof, thus impairing the function inherent in an ink jet head.